The present invention relates to a method for retrieving and storing a refrigerant while servicing a cooling or heat pump system and in particular to a passive retrieval and storage apparatus.
It is widely believed today that refrigerants, typically chlorofluorocarbons, used in vapor compression cooling and heat pump systems have a detrimental effect on the earths, atmospheric ozone layer when the refrigerant is released from the cooling system into the atmosphere. When repairing a cooling system, it is often necessary to first remove the refrigerant from the cooling system. The refrigerant can either be released to the atmosphere or it can be recovered for later use in the same equipment, or subsequent reprocessing and reuse. Because of the harmful effects associated with the release of refrigerant to the atmosphere, several devices have been developed in recent years to retrieve the refrigerant from a cooling system before it is serviced. Many of these devices, in addition to retrieving the refrigerant, also purify the refrigerant so that the refrigerant can be used to recharge the cooling system after the necessary repairs have been made.
Many of these refrigerant retrieval systems include several components typically found in cooling systems such as a compressor, condenser and evaporator. The compressor is generally used to draw the refrigerant from the cooling system into the retrieval system where it is condensed, purified and stored for later reuse and pumped back into the system being serviced. Such systems are relatively expensive and can also be difficult to transport to the job site when making a service call to repair a cooling system. For a service company having a fleet of service trucks, to equip each truck with such a recovery system can be very expensive and space consuming. The expense and transport of the recovery system may not be justified by the cost savings from reusing the refrigerant and may outweigh a desire to avoid environmental damage. As a result, many appliance repairmen may not bother to recover refrigerant from cooling systems.
Accordingly, it is an object of the present invention to provide a simplified apparatus for refrigerant retrieval that can be easily transported to the cooling system being repaired and which is less expensive than the large retrieval systems currently in use that include a compressor.
It is a feature of the retrieval and storage apparatus of the present invention to utilize the compressor of the cooling system being repaired in the retrieval process rather than including a compressor in the retrieval apparatus. The apparatus of this invention many also be employed in conjunction with an auxiliary compressor in conditions of failure of the serviced system compressor.
The apparatus of the present invention includes a coiled collector tube for receiving pressurized liquid refrigerant from the cooling system. The collector tube is contained within a well insulated evaporator housing. One end of the collector tube is connected to the high pressure side of the cooling system to receive pressurized liquid refrigerant from the condenser. The other end of the collector tube includes an adjustable metering valve leading to a refrigerant outlet that discharges refrigerant from the collector tube into the evaporator housing. The interior of the evaporator housing is connected to the low pressure side, or inlet side, of the compressor of the cooling system to draw the evaporated refrigerant into the compressor. The existing service ports on the cooling system can be the connection points.
In operation, the cooling system compressor is activated to pump condensed pressurized liquid refrigerant into both the system evaporator and the collector tube which is now functioning as a parallel evaporator. As the refrigerant passes through the metering valve into the evaporator housing, the refrigerant will flash causing the available heat to be removed within the evaporator housing. The temperature within the housing will decrease to a point where there is not enough available heat to evaporate all the liquid refrigerant entering the evaporator housing. At this point only a small portion of the refrigerant is now flashed since the only heat available is what is introduced into the evaporator housing by the sensible heat being given off from the collector tube. The warm liquid refrigerant within the collector tube is now undergoing extreme subcooling. Since the entering liquid refrigerant that does not evaporate has already been cooled to about the same temperature as the evaporator housing, it is relatively stable and will begin to collect in the bottom of the evaporator housing. It is now trapped there due to the limited heat available within it's environment.
The evaporated refrigerant picks up heat from the collector tube, as it is pulled from the evaporator housing through the outlet back into the compressor where it is pressurized and later condensed and returned to the collector tube. As the cold liquid refrigerant is trapped in the collector tube, the system pressures generated by the compressor will gradually decrease as less refrigerant becomes available for the compressor to displace. When the quantity of refrigerant leaving the device equals the quantity of refrigerant entering the device, the exit is closed trapping the evaporated refrigerant in the housing. The compressor continues to run, forcing the refrigerant gas left in the system into the collector tube where much of it will condense because of the cold environment that has been created in the evaporator housing. When the internal temperature of the device has risen to where no more condensation is possible, the saturation temperature, the inlet valve of the retrieval apparatus is closed.
At this point, 85% to 95% of the refrigerant of the cooling system has been retrieved. Additional refrigerant can be retrieved by installing a piercing valve on the cooling system line leading from the compressor outlet and connecting the piercing valve directly to a port on the evaporator housing of the retrieval device. The cooling system line downstream from and immediately adjacent to the piercing valve is pinched-off so that all of the remaining refrigerant is pumped into the retrieval device. This refrigerant is discharged into the bottom of the housing whereby the refrigerant vapor must travel through the already collected liquid refrigerant and is thereby cooled and condensed. The system compressor will pull the system into a vacuum. The cooling system can now be repaired and since all the refrigerant has been retrieved, there is no release of refrigerant to the atmosphere.
Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings.